1. Field of the Invention
The present invention relates to a package for integrated circuits and to a method of assembly thereof.
2. Related Background Art
In order to assemble an IC chip on a circuit board, the IC chip is first assembled in a resin sealed package using a lead frame such as those shown in FIGS. 1 to 5 or in a package with a hollow portion such as shown in FIG. 6.
The assembly method for resin sealed packages shown in FIGS. 1 to 5 will be described.
First, photosensor IC chips are placed on a lead frame (shown in FIG. 1) made of a thin metal plate on which a predetermined circuit pattern is formed through pressing or etching, connections are made by using bonding wires 5 (shown in FIG. 2), and the photosensor IC chips are molded with transparent thermosetting resin 6 (shown in FIG. 3). Thereafter, leads are cut and shaped into a predetermined configuration (shown in FIG. 4). This method is widely adopted because mass production is possible and soldering to a circuit board is relatively easy.
In order to package an IC having a photosensor element, a light transmissive member 9 such as shown in FIG. 5 is bonded in order to prevent damages to the light-incidence plane and eliminate unnecessary light reflection (Japanese Patent Laid-open Application No. 63-21878).
For assembly of the package shown in FIG. 6, a photosensor IC chip 4 is placed in a hollow portion 10 of a ceramic or resin mold, connections are made by using bonding wires, and the hollow portion 10 is covered with a light permissive member 9 to hermetically seal it. With this structure, a bonding margin for maintaining the hermetic seal is required, resulting in a large package size.
These conventional methods are associated with various issues to be resolved. For example, expensive metal molds are required for each type of package. Production of various types of packages requires immense investment in facilities. It takes a long time to complete a sample which requires new metal molds. Leads are likely to be broken depending upon how the package is handled. An additional process for bonding the light permissive member 9 is required and the assembly cost rises.
A package of a lead-less structure has been proposed using a both-side printed circuit board in place of a lead frame (Japanese Patent Laid-open Application No. 2-2150). However, this method uses metal molds like the above methods so that it is associated with similar problems.
It is an object of the present invention to provide an IC package and one assembly method therefor that make it possible to dispense with metal molds, render unnecessary immense investment in facilities even for production of various types of packages, are applicable to mass production with low assembly cost, and make it easy to solder an IC chip to a circuit board.
According to one aspect of the present invention is provided an IC package comprising: a substrate having recesses formed on the side wall thereof; an insulating film for covering an opening of each recess on the side of a principal surface of the substrate; and an IC chip mounted on a mount surface side of the film on the substrate, wherein a conductive portion formed in each recess is used as an external connection terminal for the IC chip.
According to another aspect of the invention is provided a method of assembling an IC package comprising the steps of: forming a substrate having a plurality of through holes each having an insulating film covering one of the openings of each through hole; mounting one or more IC chips on a principal surface of the substrate on the insulating film side, and electrically connecting the IC chip and the through holes; sealing the substrate with the IC chip mounted thereon with insulating resin; and cut the substrate with the IC chip mounted thereon to expose the side wall of each through hole.
According to another aspect of the present invention is provided an IC package comprising: a substrate having recesses formed on the side wall thereof; an insulating film for covering an opening of each recess on the side of a principal surface of the substrate; an IC chip mounted on a mount surface side of the film on the substrate; a resin portion for sealing the IC chip; and a rigid member formed on the resin portion, wherein a conductive portion formed on each recess is used as an external connection terminal for the IC chip.
It is another object of the present invention to provide an IC package comprising: a substrate having recesses on the side wall thereof, the recesses being filled with conductive material; an IC chip mounted on one principal surface of the substrate; a transparent resin portion for sealing the IC chip; and a light transmissive member formed on the transparent region portion, wherein the filled conductive material at the side wall of the substrate is used as an external connection terminal for said photosensor IC chip.
According to another aspect of the present invention is provided a method of assembling an IC package comprising the steps of: forming a substrate having a plurality of through holes each having an insulating film covering one of the through hole openings; mounting one or more IC chips on a principal surface of the substrate on the insulating film side, and electrically connecting the IC chip and the through holes; forming a light transmissive member on a transparent resin portion formed on the substrate having the IC chip mounted thereon; and cutting the substrate with the IC chip mounted thereon to expose the side wall of each through hole.
According to another aspect of the present invention is provided a method of assembling an IC package comprising the steps of: forming a substrate having a plurality of through holes each having conductive material filled in the through hole opening; mounting one or more IC chips on a principal surface of the substrate on the insulating film side, and electrically connecting the IC chip and the through holes; forming a light transmissive member on a transparent resin portion formed on the substrate having the IC chip mounted thereon; and cutting the substrate with the IC chip mounted thereon to expose the conductive material in each through hole.
According to several embodiments of the invention, thus a plurality of through holes in a printed circuit board are used as external connection terminals, instead of using conventional leads. Therefore, metal molds for lead frames are not required for each type of IC chips as in conventional cases.
Since the through hole is covered with an insulating film or filled with conductive material, resin will not flow via the through hole to the back surface of the substrate, and so it is not necessary to prepare metal molds for stopping a flow of resin.
Since the side wall of the through hole cut vertically or the conductive material in the cut through hole is used as an external connection terminal, leads are broken less than is the case with conventional leads.
If transparent resin is used when necessary and a light transmissive member having a high rigidity such as glass is placed on the transparent resin, it becomes possible to prevent damage to the surface of the transparent, resin, and becomes easy to retain optical flatness. An IC package of this invention is preferably used for optical semiconductor elements such as optical sensors, light emitting diodes, and semiconductor lasers.
Since the light permissive member is adhered at the same time as the resin is coated and cured, an increase in the number of processes can be prevented. Furthermore, since an additional margin is not necessary, the outer dimension of the IC package can be made small.